Contactor



July 22, 1947. {3. ELLIS ET'AL CONTACTOR I Filed Spt. 15, 1942 3 Shets-Sheef 1 WITNESSES:

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' ATTDORNEY Patented July 22, 1947 OONTACTOR Delbert Ellis, Forest Hills, and James H. Alspach,

Swissvale, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 15, 1942, Serial No. 458,386

7 Claims.

This invention relates to a contactor and, more particularly, to an improved arrangement and construction of operating mechanism in a circuit controlling device for moving the stationary and movable contacts thereof into and out of engagement.

One of the principal objects of this invention is to provide an improved arrangement of operating mechanism for actuating the movable contact of a circuit control device, such as a line starter, which is more compact and occupies less space than conventional prior art control devices or switches of a given rating, and in which all the parts are readily accessible and removable for the purpose of repair and inspection.

A further object is to provide electromagnetic operating mechanism for a circuit control device in which the actuating armature is positioned between the magnet core and its supporting structure.

A further object is to provide an actuating mounting for the movable contact of a circuit controller comprising a pivotally supported actuating bracket having the movable contact connected thereto at one side of its pivot and an operating armature connected to the other side of its pivot.

A further object is to provide an actuating mounting of the character referred to in which the armature is arranged in the space between the operating magnet therefor and a stationary support for such mounting.

A further object is to provide an improved pivot support for an actuating mounting of the character referred to.

Other objects and advantages of this invention will become apparent from the following description and accompanying drawings in which:

Figure l is a top plan view of a contactor constructed in accordance with the principles of this invention;

Fig. 2 is a side elevational' view of the contactor shown in Fig. 1, parts thereof being broken away and shown in section;

Fig. 3 is a sectional view taken substantially on the line IIIII-I of Fig. 2.;

Fig. 4 is an end elevational view of" the armature and its supporting bracket shown in Figs. 1 and 2;

Fig; 5 is a broken away sectional view of the magnetic" core taken substantially on the line V-V of Fig. 2;

Fig. 6' is a broken away perspective view illustrating the structural and assembly features of the pivot support for the actuating mechanism of the contactor? Fig. 7 is a broken away perspective view, parts thereof being shown in section, illustrating the manner in which the molded cross bar carrying the movable contacts forms a housing for preventing endwise movement of the pivot bar;

Figs. 8 and 9, respectively, are side elevational views, parts thereof being broken away and shown in section, illustrating the manner in which the cross bar forms a housing for the pivot bar and showing the relative positions of such parts when the contactor is in its full open position and its full closed position;

Fig. 10 is a broken away detailed bottom plan view taken from the rear of the pivot bar and illustrating the manner in which the cross bar cooperates with the supporting structure for guiding the pivotal movement of the actuating mechanism; and

Figs. 11 and 121 are detailed sectional views in side elevation, respectively showing the relative positions of the stationary and movable contacts as. the movable contacts are actuated from their full open position to their full closed position.

Referring to the drawings, the switch illustrated in Figs. 1 and 2 is a line-starter type particularly adapted for connecting an electric motor or other load across the lead lines of a source of electric power supply. The main parts of the switch from the standpoint of this invention comprise an electromagnet A mounted in spaced relation with respect to a support B, a bracket member C having an armature D connected to its lower end and a movable, contact carrying cross bar E connected to its upper end, and a pivot structure F intermediate the armature D and cross bar E. The structural features of the parts A through F and the manner in which such parts cooperate are such as to provide a switch which is smaller and more compact for a given rating and capacity than prior art constructions, contains a minimum of relatively moving parts subject to wear and likely to become out of' order, and in which all the parts are readily accessible and easily taken apartfor the purpose of inspection. or repair. This will be set forth in detail hereinafter.

The support B comprises a base member I adapted to be secured to a panelboard or in a cabinet and is preferably mounted in a vertical position as illustrated in Figs. 1 and 2. The

magnet A comprises an E-shaped laminated iron core 2 and an energizing coil 3, and. is mounted in spaced relation with respect to the base I by means of a plate 4 rigidly secured to the base member I. The plate 4 is provided with a lower pair of spaced outwardly projecting members or legs 5 and a similar upper pair of legs 6. The

core 2 is provided with openings 1 extending through the laminations thereof at the base of its outer legs which are adapted to be aligned with openings 8 in the outer ends of the legs 5 and 8. The core 2 is secured in position by means of bolts 9 which are passed through the aligned openings 1 and 8 as best shown in Fig. 1. In this manner the core 2 is secured in position with its pole faces I spaced from the base The coil 3 is secured in position on the central leg of the core 2 by means of a bolt II which is passed through aligned openings in brackets |2 connected to the coil 3 and an opening l3 extending transversely and centrally of the core 2. The opening I 3 in which the bolt II is receivable is provided by a hollow rivet M as best shown in Fig. 5. The hollow rivet |4 cooperates with the solid rivets IS in holding the E-shaped laminations of the core 2 clamped together prior to mounting of the core 2 on the legs 5 and 6 in addition to its function of forming a support for the coil 3. After mounting the core in position on the supporting legs 5 and B it will be apparent that the fastening elements 9 provide additional means for clamping the core laminations together.

Each of the upper legs 6 is provided with an upwardly extending portion or ear l6 which is shaped to define a notch (Figs. 2 and 6). The notches H are rectangular in shape to conform with the contour of the pivot bar l8 which is slidable endwise therethrough into position as best shown in Fig. 6. The pivot bar is thus supported by the legs 6 at spaced points intermediate the ends thereof and is prevented from turning movement with respect to the legs 6. A corner of the pivot bar |8 provides a knife-edge pivot l9 about which the bracket member C may pivot. Although a square pivot bar |8 has been shown, it will be understood that other shapes may be readily employed without departing from the principles of this invention, as long as such other shapes provide a knife-edge pivot |9 and have a contour which when received in the notches I"! will function to prevent movement of the pivot edge I!) with respect to the legs 6.

The bracket C comprises a channel-shaped member (Figs. 2 and 4) having arms 2| projecting upwardly from the sides thereof as best shown in Figs. 2 and 6. Referring to Fig. 6, it will be noted that the arms 2| straddle the supporting legs 6 and have a bracing member 22 connected to the upper surfaces thereof and extending transversely therebetween. The bracing member 22 is provided with lanced out parts 23 adjacent the ends of the pivot bar IS. The portions 23 are inclined angularly with respect to the upper surface of the member 22 and cooperate with such surfaces to define dihedral bearings 24 in which the knife-edge I9 is seatable. The knifeedge I9 and the apex of the dihedral bearing 24 define the center of pivotal movement of the bracket 2!. By having the lanced out portions 23 provide pivot seats at spaced points along the pivot bar l8, additional rigidity is given the con struction since such spacing of the pivot supports helps in guiding the movement of bracket C.

The bracket C is maintained in engagement with the pivot bar I8 by means of a spring 25 (Figs. 2, 6, 10). One end of the spring engages a recess 25 (Fig. 2) formed in a molded member 2'! which is secured to the base The other end of spring 25 abuts centrally against the bracing member 22. The resilient force exerted by the spring 25 functions to maintain the pivot edge |9 seated in the dihedral bearing 24 and biases the bracket member C in a counterclockwise direction to a limited position with respect to the base member Movement of the bracket C in a counterclockwise direction is limited by engagement of the lower end 20a of the bracket C with the surface of the plate 4 as best shown in Fig. 2. The point of engagement of spring 25 with the under surface of the bracing member 22 is located above and closely adjacent the pivot edge I9.

The web portion 2|] between the flanges 28 of the bracket C (Figs. 2, 4) is positioned underneath the magnet A and below the pivot bar l8. An armature 29 is mounted on the bracket C by a rivet 30 having its ends connected to the flanges 28 and extending transversely of the bracket C (Figs. 2, 3, 4). The armature 29 is mounted on the rivet 39 by means of a sleeve 3| rotatably carried by the rivet 39 and having limited engagement with the armature 29 in an annular area as at 32 (Fig. 3). Rubber bushings 33 are provided between the edge portions 34 of the armature 29 and the flanges 28 for preventing sid-ewise movement of the armature 29 on the sleeve 3|. The construction of the sleeve 3| and the manner in which it engages with the armature 29 in an annular area as at 32 allows the armature to pivot about the axis of the rivet 30 and about an axis at right angles thereto and extending 10ngitlldi nally of the armature 29. The axes of such pivotal movements lie in a common plane which is substantially parallel to the pole faces H] of the core 2 when the armature 29 is in its closed position. This movement is desirable in order that the surface 35 of the armature which engages with the pole faces l0 (Fig. 2) may align itself with the surfaces presented by such pole faces for the purpose of preventing wear. However, the mounting of the armature 29 on the sleeve member 3| is a universal mounting and permits pivotal movement of the armature about the axis 36 (see Fig. 3) in addition to the desirable movemerits mentioned above. Pivotal movement of the armature 29 about the axis 36 is undesirable since such movement will permit the end portions of the armature 29 to move from underneath the end pole faces H! at the outer ends of the core 2 and thereby result in an only partial engagement of the armature with such pole faces. To prevent rotation of the armature 29 about the axis 36 and thereby disalignment of the armature 29 with respect to the pole faces ID, the edges 34 of the armature 29 extend downwardly as at 31 (Figs. 2, 4) below the lower surface of the armature 29. The web 20 is provided with a part 38 which extends upwardly between the extensions 3'! and cooperates with such extensions to prevent rotational movement of the armature 29 about the axis 36. In this manner the longitudinal center line of the armature 29 is effectively aligned and maintained in a plane extending longitudinally and centrally of the core 2.

A molded cross bar 39 (Figs. 1, 2, 7) formed of suitable insulating material, such as Bakelite, is connected by stud bolts 49 to the upper surface of the bracing member 22 shown in Fig. 6. The cross bar 39 has a cavity 4| (Figs. '7, 8, 9) immediately below the point at which the bolts 40 (Figs. 1, 2) engage with the bracing member 22. The cavity 4| cooperates with the upper surface of the bracing member 22 to form a housing for the pivot bar l8 (Figs. 8, 9). The end surfaces 42 of such housing engage with the end surfaces 43 of the pivot bar |8 as best shown in Fig. 7 to prevent endwise movement of the pivot bar l8. In addition the longitudinal surfaces 44 of the cavity 4t function. to prevent disengagement of the pivot bar It: with; the dihedral bearing 24 providedby the upturned portion 23' of theibracing member 22, such engagement being maintainedotherwise only by the resilient bias of the spring, 25 and. the gravitational bias on the bracket C and the parts connected to the bracket. Fig. 8- shows the relative position of. the surfaces 44 of the cavity 4| when the contactors are in their full open position, and. Fig. 9- shows the position of such surfaces when the contactor is in its sealed or: closed position. Due to the relatively small clearance betweenthe cavity surfaces 44 and the pivot bar [8, it will be apparent that very little movement of the bracket C and the associated parts. with respect to the pin I8 is permitted; whenthe unit is subjected. to shock. forces.

The tapered rearportion 45 of the cross bar 39 is: provided with a recess 46 as best shown in Fig. 1.- The edges 4-! of the recess slidably engagewith the outer surfaces of th supportinglegs 6 as best shown in Fig. to guide the pivotal movement of the cross bar and connected bracket C with respect to the leg 6'. In this manner metal-to-metal engagement of the flange mem bers 21 with the supporting leg 6' during pivotal movement of the bracket C is efiectively' prevented.

The contactor orline starter illustrated is of the multiple break type and the cross bar 39; is provided with three fingers 48 (Fig. 1). Each finger- 48 is provided with a bridging member 49 carrying a pair of movable contacts 50 for engaging a pair of stationary contacts 51 to complete a circuit connected to such stationary contacts. The stationary contacts 5| are carried by the molded base 21 of insulating material which is secured to. the'base l. by a pair of bolts 52' (Fig; I). As best shown in Figs. 1 and 2 the bridging member 49* is mounted in a carrier member or saddle 53 of rectangular shape fastened by a screw 54 to an end; of one of the arms 48. A spring 55 is provided for maintaining the. bridging member 49 against the base of the saddle 53. The spring 55 is compressible to permit relative movement between the bridging member and the saddle'53.

As best shown in Fig. 2 the bridging member 49 is provided with shoulder portions 56': intermediate the contacts '50 which are engageable with the edges 51 defining the openings in. the saddle 53 through which the ends of the. member 49' project for the purpose of preventing longitudinal movement of the bridging member 49 with respect to the saddle 53. However, due to the softness of the material from which the bridging member 49 is formed, the shoulder portions 56 would be worn. away if the weight of the bridging member were carried thereby when it occupies a vertical position as shown in Fig. 2'. To prevent the entire weight of the member 49 being carried by' the edges 51, the springs 55 are arranged on a bias with respect to the member 50' as best shown in Figs. 11 and 12. In this manner the springs 55 exert an upward force on the bridging member 49 to maintain the upper set of shoulders 56 out of engagement with the edges 51.

Since the movable contacts 50' are made out of relatively soft material such as silver, a wiping action or relative sliding movement between the contacts 50 and 5! would be apt to cause a rapid wearing of the contacts. The construction of the stationary contacts and the mounting for the movable contacts 50 comprising the saddle 53 and. finger 48 is effective to prevent such wipiii ing action. Referring to. Fig. 2, it will, be noted that the: surfaces of the stationary contacts 51 lie in: a plane which passes; through the: axis of the, pivotbearing 24" for the actuating mechanism for the movable contacts. The surfaces of the movable contacts 50. lie, in a plane which passes through the same; pivot axis. In this manner, as the; bracket C is pivoted, to closed position; both movable contacts 50 on the bridging member 49 willbe'moved'; to a position in which the contacts 50* engage the stationary contacts 5| at'substantially the same time. Consequently, no wiping action of the contacts occurs when they are moved, into and out of engagement. Fig. 11 shows the position of the stationary contacts 50 in their fully open. position, and the dotted lines show the: position: of" the bridging member 50 at the time the movable contacts initially engage with therstationar contacts 5 I After initial engagement of the; contacts it is desirable that movement of the finger 4.8 be continued toinsure a sufiicient contact pressure. This. isaccomplished by a compression ofthe sprlng 55; as the finger 48 moves to the position shown in Fig.. 12 inwhich the armature 29 is in its fully closed position. Duringthis overtravel movement of the actuating mechanism, it is also desirable that wiping action of the contacts be prevented. Since the finger 48 and the parts connected: therewith move. on an arcuate path, the engagement of themember 53 with the shou-l dersr56 mlght cause sucha wiping movement. To prevent this, the upper edge 58 of the carrier member 53 is made longer than the lower edge 59. Consequently, as the member 53v moves beyond the poi-ntof initial engagement of the movable contact 50- with the stationary contacts 5|, the upper edge 58. will move farther than the lower edge 59; Accordingly, as the finger 48 moves intothe position shown in Fig. 12, it will be apparent that av foreshortening of the portion of the member 53' between the shoulders 5.6 will be-had. That is, the clearance between the shoulders 56 and the edges 58 and 59 will be increased. The member 53 is thus prevented from imparting further movement to the bridging member 50 while: the mechanismmoves from the initial contact position. into the overtravel position shown in 12-.

Thepole faces, ll! of the core 2 (Fig. 2) are positioned in, a plane containing the knife-edge I'9 of the pivot bar I18.v The armature 29 is mounted on. the bracket C in such manner that its surface 35 is always positioned substantially in a plane which contains the knife-edge l9 and rotates, about the pivot axis at 24, to a position in. which the armature surface 35 engages the pole faces 0;. By virtue of this location of the knife-edge pivot IS with respect to the pole faces I'll of the core 2 and the armature surface 35, the armature is moved into and out of engagement with, the magnet poles without relative sliding movement between the armature and pole surfaces thus avoiding the frictional wear otherwise apt to occur. Since the mounting of the armature Won the bracket C permits relative pivotal movement with respect thereto, as pointed out above, it will be apparent that the armature 29 will be pivoted in a counterclockwise direction about the axis of the rivet 30 as it is moved to closed position due to the greater magnetic attraction on the upper end of the armature as viewed in Fig, 2. Consequently, the upper end of the armature 29 will strike the upper pole face I0 first as viewed in Fig. 2. After striking the upper pole face It], the armature will then fulcrum about its point of initial engagement in a clockwise direction to a position in which the surface 35 is also engaged with the other pole faces. The upper leg of the core 2 is rounded as at 63 (Fig. 2) at the point of initial engagement in order to facilitate the final fulcruming movement of the armature 29. This final fulcruming movement takes place without sliding of the armature surface 35 over the pole faces ID as it would occur if the pivot axis 24 were located substantially out of the plane containing the pole faces l0.

An arc extinguishing structure indicated as a whole by the numeral 60 is employed in connection with the stationary and movable contacts (Figs. 1, 2). This structure is described more in detail in the copendin application of J. D. Ellis and O. L. Taylor, Serial No. 509,260, filed November 6, 1943. An arc control and limiting device indicated as a whole by the numeral BI is employed in connection with the arc extinguishing structure 50, the control device 6| being disclosed more in detail in the copending application of J. D. Ellis and O. L. Taylor, Serial No. 453,058, filed July 31, 1942, which became Patent No. 2,356,039 on August 15, 1944.

The parts thus far described are readily assembled by first securing the plate 4 and the molded member 21, with the stationary contacts 5| in position thereon, to the base plate I. The spring 25 is then placed in the recess 26 and the bracket C is placed in position with its attached armature D positioned between the legs 5 and 6 carried by the plate 4, so that the bracing member 22 (Fig. 6) extends over the spring 25. Pressure is then applied to the bracing member 22 so as to compress the spring 25 in order to clear the bracing member 22 of the pivot bar openings IT. The pivot bar l8 may then be moved endwise into position through the openings l1. Upon releasing the pressure on the bracing member 22, the spring 25 will function to move the bracket C into its limited open position as shown in Figs. 2 and 6. The core 2 with its coil 3 mounted thereon is then placed between the spaced legs 5 and 6 carried by the plate 4 and secured in position by the two fastening bolts 9. The movable contactcarrying cross bar E is then placed in position over thepivot bar l8 and is secured in position by the two stud bolts 40 (Fig. 2) which are threaded into suitable threaded openings of the bracing member 22. The assembly of the switch is completed by fastening the arc extinguishing structure 6!! on the molded base 21 by screwing two stud bolts 54 into threaded openings 65 of the molded member 21 (Fig. l)

It will be noted that the manner in which the switch of this invention is assembled makes all the parts thereof readily accessible for the purpose of repair and inspection. Moreover, such parts are secured together with a minimum of fastening elements and the switch may be readily taken apart in a minimum of time for replacing any defective part. It will be particularly noted that the mounting of the magnet A in spaced relation with respect to its support B makes the magnet A accessible and removable without the necessity of disturbing the armature D which is positioned between the magnet A and the support B. This eliminates an undesirable feature of conventional electromagnetic switches which require the removal of the armature in order to have access to the magnet. The advantage of having the magnet A removable without disturbing the armature D will be appreciated from the fact that the magnet is the element most likely to get out of working condition.

The mounting of the armature A in spaced relation to its support B affords another essential advantage. This mounting cooperates with the arrangement of the bracket C and pivot F to reduce the physical size of a switch having a given capacity and rating. By reason of the location of the bracket C and the armature D between the magnet A and support B, together with the pivot F, the operation of the magnet A has the efi'ect of moving the armature D and the movable contacts in opposite direction with respect to the support B. In this manner the movable contacts travel in the same direction toward the stationary contacts in response to operation of the electromagnet as in the case of conventional electromagnetic switches with a magnet positioned between the armature and its support. However, in these conventional constructions a larger amount of space is required to allow for movement of the movable contacts into engagement with the stationary contacts, since the pivotally movable contact carrier has a radius of movement considerably longer than that of the cross bar E of this invention. In other words, the mounting of the armature A according to this invention permits the pivot F to be located closer to the base B thereby reducing the overall size of the switch.

The particular arrangement of the bracket C and pivot structure F of this invention also affords the use of a smaller magnet for a switch having a given are rupturing capacity. This permits the kick-out spring 25 to be located closely adjacent the axis of pivotal movement. In this manner the lever arm provided by the bracket C above the pivot F for compressing the kickout spring 25 is extremely short as compared with the lever arm below the pivot F to which the operating magnetic force is applied. Accordingly, the strength of the magnetic force for moving the armature to its closed position need not be as large as in known switches of comparable rating and a smaller magnet may be used. In addition the location of the sprin 5 ad t the pivot F provides a shorter resilient lever arm as compared to the lever arm on which the movable contacts 50 are mounted. In this manner a small resilient biasing kick-out force is multiplied to enable the drawin of a larger arc than would otherwise be the case.

Since numerous changes may be made in the above described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limitin sense.

We claim as our invention:

1. In an electric switch, a support, a plate mounted on said support and having upper and lower pairs of spaced legs projecting outwardly therefrom, an electromagnet secured to the outer ends of said legs and spaced from said plate, an elongated pivot bar extending transversely of said upper pair of legs and having a longitudinal pivot edge, a bracket having upwardly projecting parts defining dihedral bearings at spaced points intermediate the ends thereof, a spring engageable with one end of said bracket for biasing the same to a limited position with respect to said support and for maintaining said bearings in engagement with said edge, the other end of said bracket projecting downwardly into the space between said magnet and support, an armature for said magnet mounted on said other end, and a cross-bar connected to the first-named end of said bracket and forming together with said bracket a housing for said pivot bar, said housing having surfaces operative to prevent endwise movement of said pivot bar and to limit movement of said cross-bar and bracket with respect to said pivot bar.

2. In an electric switch, a support, an electromagnet having pole faces mounted on said support, a pair of stationary contacts mounted on said support, a bracket having a pivot on said support, the axis of said pivot and said pole faces and the surfaces of said contacts being located substantially in a common plane, an armature connected to one end of said bracket for engagement with said pole faces, a pair of movable contacts connected to the other end of said bracket for engagement with said stationary contacts, the pole-face engaging surface of said armature and the surfaces of said movable contacts being located in a common plane passing through said pivot axis.

3. An electric switch, comprising a support, a pair of stationary contacts mounted on said support, a pair of movable contacts, mounting means for said movable contacts comprising an arm pivotally connected at one end to said support, a substantially U-shaped saddle secured to the other end of said arm, a bridging member mounted on said saddle and carrying said movable contacts, a spring for biasing said bridging member toward the base of said U-shaped saddle, said pairs of contacts being arranged so that the contacts of each pair are spaced from each other in a radial direction relative to the pivot axis of said arm and in a plane extending substantially through said axis in order to effect simultaneous engagement and disengagement of each of said movable contacts with said respective stationary contacts, said bridging member having shoulders engageable with said saddle to limit endwise movement of said bridging member with respect to said saddle, said saddle being shaped to move away from said shoulders upon pivotal movement of said arm after initiation of contact engagement between said contact pairs so as to then permit a larger extent of endwise movement of said bridging member.

4. In a switch as claimed in claim 3, said arm and said bridging member being disposed so as to extend in a generally vertical direction upon installation of the switch, and said spring being arranged on a bias so that its force has an upward component preventing the weight of said bridging member from being carried by said shoulders.

5. An electric switch, comprising a, pair of stationary contacts, a pair of movable contacts to engage said stationary contacts respectively, an arm pivoted at one end, a saddle mounted on the other end of said arm, a bridging member movably seated in said saddle and carrying said movable contacts at opposite sides of said saddle, said bridging member extending substantially radially relative to the pivot axis of said arm and having shoulders at both sides respectively of said saddle, said saddle having edges extending normally at an acute angle relative to said bridging member for engaging said respective shoulders to limit radial movement of said bridging member, the edges of said saddle at the side away from said axis being longer than the edges closer to said axis so that the angle between said saddle edges and said bridging member is increased during movement .of said arm beyond the position Where said movable contacts initially engage said stationary contacts so as to then permit a larger extent of radial movement of said bridging member, and resilient means for biasing said bridging member toward the base of said saddle.

6. In an electric switch, a support, a pivot bar having a pivot edge, said support having two parallel parts spaced from each other and provided with aligned notches respectively into which said pivot bar is insertable, said notches and the portion of said bar positioned therein being shaped to prevent turning movement of said bar, a movable switch member having two dihedral pivot bearings spaced from each other and disposed for engaging said edge in order 'to permit limited rotation of said member about said edge, and resilient means disposed between said support and said member so as to exert a force on said member and pivot bar toward said notches while biasing said member to a given angular position with respect to said support.

7. In an electric switch, a support, a pivot bar having a pivot edge, said support having two parallel parts spaced from each other and provided with aligned notches respectively into which said pivot bar is insertable, said notches and the portion of said bar positioned therein being shaped to prevent turning movement of said bar, a movable switch member having an insulating body and two pivot bearings connected with said body and spaced from each other for engaging said edge to permit limited rotation of said member about said edge, said body having a cavity substantially surrounding said bar to prevent excessive motion of said pivot bearings away from said edge and forming two end Walls engageable with the respective ends of said bar to prevent endwise movement of said bar, and spring means disposed between said support and said member for biasing said member toward said bar in the direction toward said notches.

DELBERT ELLIS. JAMES H. ALSPACH.

REFERENCES CITED The following references are of record in the file of this patent:

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